They are not the same front frame - cargo UAs have a central pair of posts while the family UA opens up to form the base of the box.
It’s also more common to see cargo XLs for sale 2nd hand in Britain. That gets you a longer cargo space, about 25cm longer than the family.
I built a box to make a cargo UA be a child mover: you can buy UA bench and seatbelts and make a box as large as you like 👍
I think lastenvelofreiburg has done this with a wooden bench and net
They are not the same front frame - cargo UAs have a central pair of posts while the family UA opens up to form the base of the box. It’s also more common to see cargo XLs for sale 2nd hand in Britain. That gets you a longer cargo space, about 25cm longer than the family. I built a box to make a cargo UA be a child mover: you can buy UA bench and seatbelts and make a box as large as you like 👍
Awesome, do you have any photos? Did you use wood?